A geothermal production pump is used to extract geothermal fluid from a deep well. A typical downhole geothermal production pump is a vertical turbine pump which has three main parts: the head assembly which comprises the motor for driving the pump, the shaft and column assembly, and the pump bowl assembly. The lower pump bowl assembly comprises the stationary bowl and the impeller which rotates within the bowl for enhancing the flow of the fluid to be extracted. The shaft and column assembly provides the connection between the head assembly and the pump bowl assembly. The line shaft transmits torque from the pump motor to the impellers and rotates internally to the column. The extracted fluid is transported within the discharge column to the surface.
Due to the high temperature and pressure of the geothermal fluid, a bearing mounted on the line shaft is subjected to considerable wear. To prevent excessive wear to the bearing mounted on the line shaft, the line shaft rotates within a lubrication column through which oil flows. However, the line shaft and bearings are prone to damage as a result of the intrusion of the high-pressure geothermal fluid into the lubrication column. In particular, non-condensable gases (NCG's) present in the geothermal fluid, especially when the geothermal fluid contains a large amount of NCG's, are liable to infiltrate into the lubrication column, causing sluggish oil flow and even damage to the pump as a result of repeated cycles of bubble formation and cavitation.
It is an object of the present invention to provide an apparatus for maintaining operation of a geothermal production pump when extracting geothermal fluid having a relatively high NCG content.
Other objects and advantages of the invention will become apparent as the description proceeds.